Cleaning articles impregnated with detergent are well known and have existed in the household cleaning market for ages. The most familiar and perhaps the oldest of these products is the steel wool pad having a soap core. More recent inventions include “pre-moistened” articles such as the popular and convenient hard surface disinfecting cleaning wipes along with many personal cleansing products. Other cleaning, personal cleansing, or scrubbing articles may be substantially dry rather than pre-moistened, (i.e. the cleaning composition is dried and impregnated within the article), in which case the consumer wets the product prior to use. These are often referred to as “water-activated” articles. Many recent cleaning articles have appeared that are used in conjunction with a mop handle/tool for floor cleaning.
One problem that has persisted with detergent-impregnated metal wools, synthetic pads, sponges, scrubbing articles, and the like, is maximizing the length-of-life of the detergent expressed from the cleaning article throughout multiple cleaning tasks while still delivering an efficacious level of detergent from the article for any single cleaning task at hand. To maximize consumer acceptance, a detergent-impregnated cleaning article should last for at least a few cleaning chores before the detergent is gone and the pad disposed of. This is important even for “disposable articles” since it is unlikely that a consumer will use the product for one small task (e.g., cleaning one bathroom sink) prior to its disposal. It is more likely that a consumer will wet the article and use it for multiple cleaning tasks, such as cleaning dual sinks, the shower and the tub within a bathroom, and will expect the cleaning article to keep delivering detergent during this multiple task cleaning session.
To this end, researchers in this field have included polymeric additives to extend the life of the detergent in the article through multiple uses. Their efforts seem to be more empirical rather than theoretical, since there seems to be little thought given to chemical structures and the possibility of “binding” detergent ingredients to the fibers of the scrubbing article. Polymeric additives, selected only empirically as “thickeners”, may need to be incorporated at high levels to have any effect on extending the life of the detergent, and may actually reduce overall detergency of the composition. At the very least, some polymers are expensive additives that should be added sparingly.
For example, U.S. Pat. No. 3,788,999 to Abler claims a long-life sudsing blend for use in a scrubbing pad that comprises a hydrophilic proteinaceous colloidal agglutinant such as gelatin or casein. The amount of this material must be at least 6% by weight. The disclosure notes that for even longer detergent life, up to 50% by weight may be included at which point no further improvement is noted.
U.S. Pat. No. 4,145,302 to Doan claims a detergent pad with longer lasting detergency made possible by simply choosing less water-soluble detergent ingredients. For example, the compositions described in '302 may include the less soluble calcium dodecylbenzene sulfonate along with the more water-soluble sodium salt. This strategy would seem to jeopardize cleaning performance.
U.S. Pat. No. 4,189,395 to Bland claims the use of an acrylic latex emulsion for binding the nonionic detergent mixture within a cleansing pad. The compositions require enormous amounts of acrylic resin that contribute no detergency power to the composition, but instead only binding ability.
U.S. Pat. No. 5,507,968 to Palaikis claims the use of polyacrylamide to bind a detergent composition into a cleansing article to achieve a controlled detergent release. Polyacrylamide is relatively expensive and has no detergency or other benefit to the cleaning.
U.S. Pat. Nos. 6,573,232 and 6,794,353 to Thomas et al. claim use of a cellulosic polymer to “regulate and slow the release of the cleaning composition from the water insoluble substrate”, (see Column 8, Lines 24-26 in '232 and Column 8, Lines 42-44 in '353). The disclosure is narrowly limited to mixtures of methyl cellulose and hydroxypropyl methyl cellulose as obtained through the incorporation of various grades of Methocel®, available from Dow Chemical. These materials have historically been used for compounding slow release pharmaceuticals and for conventional rheology modification (i.e., thickening).
Accordingly, there continues to be interest in cleaning articles that are efficient at cleaning and that can be used for several cleaning tasks within a cleaning session before disposal. Also, there is a clear need for improved methods for manufacturing such articles. Substantially dry articles would improve shipping weights and the overall sustainability of products, and would allow extended shelf life and added storage convenience for the consumer.